Fast optical switch

ABSTRACT

A fast optical switch and networks comprising fast optical switches are disclosed herein. In an example embodiment, a fast optical switch includes two or more fabric switches; a first selector switch; and a second selector switch. The first selector switch may selectively pass a signal to one of the two or more fabric switches. The one of the two or more fabric switches may act on the received signal to provide a switched signal and the second selector switch may selectively receive the switched signal provided by the one of the two or more fabric switches. A slot of the fast optical switch comprises a transmission window of one of the two or more fabric switches that occurs in parallel with at least a portion of a reconfiguration window of the other of the two or more fabric switches.

CROSS-REFRENCE TO RELATED APPLICATIONS

This application claims priority to Greek Application No. 20200100439,filed Jul. 24, 2020, the content of which is hereby incorporated byreference herein in its entirety.

BACKGROUND

Datacenters are the storage and data processing hubs of the internet.The massive deployment of cloud applications is causing datacenters toexpand exponentially in size, stimulating the development of fasterswitches in order to cope with the increasing data traffic inside thedatacenter. Current state-of-the-art switches are capable of handling12.8 Tb/s of traffic by employing application-specific integratedcircuits (ASICs) equipped with 256 data lanes, each operating at 50Gb/s. Such switch ASICs typically consume as much as 400 W, whereas thepower consumption of the optical transceiver interfaces attached to theASIC is comparable.

To keep pace with traffic demand, switch capacity has to be doubledapproximately every 2 years. So far, this rapid scaling was possible byexploiting advances in complementary metal-oxide-semiconductor (CMOS)manufacturing, collectively described by Moore's law (i.e., theobservation that the number of transistors in a dense integrated circuitdoubles about every two years). However, in recent years there arestrong indications of Moore's law slowing down, which raises concerns asper the capability to sustain the target scaling rate of switchcapacity. Alternative technological approaches have been identified,such as the co-integration of photonics and electronics in multi-chipmodules, which are expected to enable the development of datacenterswitches with up to 100 Tb/s capacity. However, it is expected thatfurther scaling will not be possible in a way that is viable from thetechnological, economic, and power consumption perspective.

BRIEF SUMMARY

Various embodiments provide a fast optical switch configured to providea high capacity throughput. In various embodiments, the length of theguardband is approximately and/or substantially equal to thereconfiguration time of a selector switch (i.e., significantly shorterthan the reconfiguration time of a fabric switch. The reconfigurationtime of a selector switch is referred to as a switching time herein. Forexample, the fast optical switch is an optical switch that may beimplemented to have a link usage of greater than 90%. For example, thefast optical switch may be implemented to have a link usage of greaterthan 95%. For example, the fast optical switch is configured to minimizethe effect of reconfiguration time on the link usage of the switch.

In various embodiments, the fast optical switch comprises first andsecond fabric switches and first and second selector switches. The firstand second selector switches have a switching time that is smallerand/or shorter than the reconfiguration time of the first and secondfabric switches. For example, the first and second fabric switches mayhave a reconfiguration time that is at least one order of magnitude(e.g., at least a factor of ten) greater than the switching time of thefirst and second selector switches. The first and second selectorswitches are configured to selectively pass and receive, respectively, asignal to one of the first fabric switch or the second fabric switch.For example, the first and second selector switches may cause a firstsignal to be provided through the first fabric switch during a firstslot and then cause a second signal to be provided through the secondfabric switch during an immediately succeeding second slot. The secondfabric switch may be reconfigured during the first slot and the firstfabric switch may be reconfigured during the second slot. Thus, theguardband may be reduced to the switching time of the first and secondselector switches, which is significantly less (e.g., at least an orderof magnitude less) than the reconfiguration time of the first and secondfabric switches. fast optical switch

According to a first aspect of the present disclosure, a fast opticalswitch is provided. In an example embodiment, the fast optical switchcomprises two or more fabric switches; a first selector switch; and asecond selector switch. The first selector switch is configured toselectively pass a signal to one of the two or more fabric switches.Based at least in part on the current permutation of the one of the twoor more fabric switches that received the signal, the one of the two ormore fabric switches provides a switched signal to the second selectorswitch and the second selector switch is configured to selectivelyreceive the switched signal provided by the one of the two or morefabrics switches.

In an example embodiment, the two or more fabric switches have areconfiguration time and the first selector switch and the secondselector switch have a switching time, wherein the reconfiguration timeis longer than the switching time. In an example embodiment, thereconfiguration time is the (longest) time required for one of the twoor more fabric switches to reconfigure its internal parts in order toimplement a different permutation. In an example embodiment, a slot ofthe fast optical switch comprises a transmission window of one of thetwo or more fabric switches that occurs in parallel with at least a partof reconfiguration windows of the other of the two or more fabricswitches. In an example embodiment, the two or more fabric switches havea reconfiguration time and a slot of the fast optical switch issubstantially equal to or less than the reconfiguration time. In anexample embodiment, the two or more fabric switches comprise n fabricswitches (n an integer greater than or equal to two) and the slot of thefast optical switch is substantially equal to the reconfiguration timedivided by (n−1). In an example embodiment, each of the two or morefabric switches, the first selector switch, and the second selectorswitch is an optical switch. In an example embodiment, each of the twoor more fabric switches comprises a collection of switches arranged in amatrix configuration. In an example embodiment, a guardband of the fastoptical switch is approximately and/or substantially equal to theswitching time of the first and second selector switches. In an exampleembodiment, the first and second selector switches are configured toselect a fabric switch of the two or more fabric switches responsive toat least one of (a) an electrical or optical signal or (b) a wavelengththat characterizes a signal to be provided/received responsive to theselection. In an example embodiment, the two or more fabric switches areeach configured to reconfigure to a particular permutation responsive toan electrical or optical signal indicating the particular permutation.

According to another aspect of the present disclosure an optical networkis provided. In an example embodiment, the optical network comprises atleast one optical transmitter element; at least one optical receiverelement; and at least one fast optical switch disposed in an opticalpath between the at least one optical transmitter element and the atleast one optical receiver element. In an example embodiment, the atleast one fast optical switch comprises two or more fabric switches; afirst selector switch; and a second selector switch. The first selectorswitch is configured to selectively pass a signal (e.g., provided by theat least one optical transmitter element) to one of the two or morefabric switches. Based at least in part on the current permutation ofthe one of the two or more fabric switches that received the signal, theone of the two or more fabric switches provides a switched signal to thesecond selector switch. The second selector switch is configured toselectively receive the switched signal provided by the one of the twoor more fabric switches and provide the switched signal to at least oneoptical receiver element.

In an example embodiment, reconfiguration of the two or more fabricswitches is characterized by a reconfiguration time and reconfigurationof the first selector switch and the second selector switch ischaracterized by a switching time, wherein the reconfiguration time islonger than the switching time. In an example embodiment, thereconfiguration time is the (longest) time required for a fabric switchof the two or more fabric switches to reconfigure its internal parts inorder to implement a different permutation. In an example embodiment, aslot of the fast optical switch comprises a transmission window of oneof the two or more fabric switches that occurs in parallel with at leasta part of reconfiguration windows of the other of the two or more fabricswitches. In an example embodiment, the two or more fabric switches havea reconfiguration time and a slot of the fast optical switch issubstantially equal to the reconfiguration time. In an exampleembodiment, the two or more fabric switches comprise n fabric switches(n an integer greater than or equal to two) and the slot of the fastoptical switch is substantially equal to the reconfiguration timedivided by (n−1). In an example embodiment, each of the two or morefabric switches, the first selector switch, and the second selectorswitch is an optical switch. In an example embodiment, each of the twoor more fabric switches comprises a collection of switches arranged in amatrix configuration. In an example embodiment, a guardband of the fastoptical switch is approximately and/or substantially equal to theswitching time of the first and second selector switches. In an exampleembodiment, the first and second selector switches are configured toselect a fabric switch of the two or more fabric switches responsive toat least one of (a) an electrical or optical signal or (b) a wavelengththat characterizes a signal to be provided/received responsive to theselection. In an example embodiment, each of the two or more fabricswitches is configured to reconfigure to a particular permutationresponsive to an electrical or optical signal indicating the particularpermutation.

BRIEF DESCRIPTION OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a block diagram of an example fast optical switch according toan example embodiment;

FIG. 2 is a diagram illustrating conventional slot timing for an opticalswitch;

FIG. 3 is a diagram illustrating slot timing for a fast optical switchaccording to an example embodiment;

FIG. 3A is a diagram illustrating slot timing for a fast optical switchaccording to another example embodiment; and

FIG. 4 is a block diagram of a portion of a network comprising a fastoptical switch according to an example embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Indeed, these inventions may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout. As usedherein, terms such as “top,” “about,” “around,” etc. are used forexplanatory purposes in the examples provided below to describe therelative position of certain components or portions of components. Asused herein, the terms “substantially” and “approximately” refer totolerances within manufacturing and/or engineering standards.

As noted above, scaling of datacenter switch capacity to expecteddatacenter requirements poses a technical problem. Optical switching isgaining traction as a candidate enabling technology, owing to thetechnology's potential for very high data capacity and low powerconsumption. Optical switching introduces the notion of devices calledoptical switches, which feature optical input and output ports and arecapable of routing the light that is coupled to their input ports to theintended output ports on demand, according to one or more controlsignals (electrical or optical). Routing of the signals is performed inthe optical domain, i.e., without the need for optical-electrical andelectrical-optical conversion, thus bypassing the need forpower-consuming transceivers. Header processing and buffering of thedata is not possible in the optical domain and thus, packet switching(as it is realized in the networks that consist of electrical switches)cannot be employed. Instead, the circuit switching paradigm is used: anend-to-end circuit is created for the communication between two devices.The vast majority of optical switching network proposals follow theTime-Division Multiple Access (TDMA) approach; the time is divided intoslots. Each slot comprises a transmission window and a guardband. Thetransmission windows are used for data transmission and the guardbandsprovide time for the optical switch to be reconfigured between packets.Effectively, the network pauses during the guardbands to enable theoptical switch to reconfigure. The duration of the slots is dictatedmainly by the reconfiguration capabilities of the optical switch.

The optical networks that are designed to use optical switches work in aslotted manner: the time is divided into slots comprising transmissionwindows and dead time (guardbands) between the transmission windowswithin which data is transmitted. Each optical switch has a non-zeroreconfiguration time and during this reconfiguration time data cannottraverse the optical switch. The reconfiguration time of a switch is thetime needed for the optical switch to “re-organize” its internal partsin order to implement different permutations (i.e., connections amongthe inputs and the outputs of the switch). Thus, during thereconfiguration time, data transmission from the devices connected tothe optical switches is not permitted. In order to achieve a reasonablenetwork utilization, the slot time is generally defined as at least tentimes the reconfiguration time. For example, 90% of the time datatransmission is permitted while for 10% of the time it is not permittedbecause of reconfiguration (e.g., the slot is 90% transmission windowand 10% guardband). Thus, conventionally, optical switched networks onlypermit 90% link utilization in order to maintain reasonable slotduration. This fact has severe consequences on the performance of thenetwork. For a reconfiguration duration of 1 μs, the slot becomes 10 μs,which is much longer than the time needed to transmit an Ethernet orInfiniBand packet. Thus, the conventional networks suffer from technicalproblems of high latency and low utilization for a variety of trafficpatterns, and usually 5%-10% of the time is not used for datatransmission.

Various embodiments provide technical solutions to these technicalproblems. In particular, various embodiments provide an optical switchthat minimizes the duration of the slot in optical switching networks byreducing, minimizing, and/or eliminating the need for the pausing of thenetwork's operation during the reconfiguration of the optical switches.For example, the size of the slot may be reduced by removing theguardband from the slot and/or defining a slot that is approximatelyequal to the length of the transmission window. Various embodimentsenable the use of short slots (e.g., slots that are approximately 0.5 to8 μs long), which enables better network utilization. Moreover, variousembodiments serve to reduce the latency of the network. As such, thevarious embodiments described herein improve the operation of networksthat employ optical switches.

FIG. 1 illustrates an example fast optical switch 100 of an exampleembodiment. In various embodiments, a fast optical switch 100 comprisesa first fabric switch 104A, a second fabric switch 104B, a firstselector switch 102A, and a second selector switch 102B. In variousembodiments, the fast optical switch 100 is an integrated switch (e.g.,hybridly integrating different types of switches) or a subsystem thatcombines separate switch modules. The first fabric switch 104A is inelectrical or optical communication with a first fabric switchcontroller via an optical or electrical line 108A such that the firstfabric switch 104A may be reconfigured (e.g., through application of acontrol signal via the optical or electrical line 108A). The secondfabric switch 104B is in electrical or optical communication with asecond fabric switch controller via an optical or electrical line 108Bsuch that the second fabric switch 104B may be reconfigured (e.g.,through application of a control signal via the optical or electricalline 108B). For example, the first and second fabric switches 104A, 104Bmay be configured to reconfigure to a particular permutation responsiveto an electrical or optical signal indicating the particular permutationand passed to the respective switch via the corresponding optical orelectrical line 108A, 108B. The first selector switch 102A is inelectrical or optical communication with a first selector switchcontroller via an optical or electrical line 106A such that the firstselector switch 102A may be reconfigured (e.g., through application of acontrol signal via the optical or electrical line 106A). For example,the first and second selector switches 102A, 102B may be configured toswitch between providing and/or receiving signals to/from the first orsecond fabric switch 104A, 104B responsive to an electrical or opticalsignal passed to the respective switch via the corresponding optical orelectrical line 106A, 106B.

In various embodiments, the first and second fabric switches 104A, 104Bare fabric switches. For example, each of the first and second fabricswitches 104A, 104B may comprise a collection of switches arranged in amatrix configuration. For example, the first and/or second fabric switch104A, 104B may be a crossbar switch. The first fabric switch and thesecond fabric switch may have similar or substantially equalreconfiguration times. For example, the first fabric switch and thesecond fabric switch may have a reconfiguration time t₁, which is thetime required for internal parts of the corresponding fabric switch tobe reconfigured in order to implement a different permutation of theswitch (e.g., connecting of an input to a desired output, and/or thelike). In an example embodiment, the fast optical switch 100 maycomprise more than two fabric switches 104. In various embodiments, thetwo or more fabric switches 104 may have the same blockingcharacteristics and/or the same number of input and/or output ports. Invarious embodiments, the fast optical switch 100 may have differentfunctionality, connectivity, blocking characteristics, input and/oroutput ports, and/or the like.

In various embodiments, the first and second selector switches 102A,102B are configured to select between the first fabric switch 104A andthe second fabric switch 104B. In an example embodiment, the first andsecond selector switches 102A, 102B are space switches, meaning that theoutput port (e.g., fabric switch 104) is chosen by reconfiguring theinternal parts of the selector switch 102. For example, theconfiguration of the internal parts of the selector switch 102 maydetermine which of the fabric switches 104 the selector switch 102provides a signal to and/or receives a signal from. In variousembodiments, a selector switch 102 may amplify a signal. For example, inan example embodiment, a selector switch 102 may be implemented with acoupler and two or more semiconductor optical amplifiers (SOAs) (e.g., nSOAs).

In an example embodiment, the first and second selector switches 102A,102B are passive wavelength switches, meaning the output port isselected based on the optical wavelength of the signal. For example, atransmitter may comprise and/or be in communication with a tunable laserand/or multiple lasers of different wavelengths. The wavelength of lightused by the transmitter to provide the signal (e.g., the wavelength thetransmitter causes the tunable laser and/or two or more lasers ofdifferent wavelengths to emit the signal at) is determined by the fabricswitch 104 that the signal is to be processed and/or passed through. Forexample, for an optical switch comprising two fabric switches 104, thetransmitter may cause a signal characterized by a first wavelength to beprovided to the fast optical switch 100 during a first slot and a signalcharacterized by a second wavelength to be provided to the fast opticalswitch 100 during a second (consecutive) slot, wherein the firstselector switch 102A provides the signals to one of the first or secondfabric switches 104A, 104B based on wavelength characterizing thesignal. In another example, for an optical switch comprising threefabric switches 104, the transmitter may cause a signal characterized bya first wavelength to be provided to the fast optical switch 100 duringa first slot, a signal characterized by a second wavelength to beprovided to the fast optical switch 100 during a second (consecutive)slot, and a signal characterized by a third wavelength to be provided tothe fast optical switch 100 during a third (consecutive) slot, whereinthe first selector switch 102A provides the signals to one of the first,second, or third fabric switches 104 based on the wavelengthcharacterizing the signal. As should be understood, in these examples,the first, second, and third wavelengths are different wavelengths. Forexample, the first selector switch 102A may be a passive arrayedwaveguide grating (AWG) demultiplexer and/or the second selector switch102B may be a passive AWB multiplexer. In such an example, the switchingtime is dictated based on the tuning time of the tunable laser. In anexample embodiment, the tuning time of the tunable laser is on thenanoseconds scale. Thus, the switching time using passive waveguideselector switches is significantly shorter than the reconfiguration timeof the fabric switches 104.

In various embodiments, the first and second selector switches 102A,102B have a switching time that is significantly short than thereconfiguration time of the first and second (and any additional) fabricswitches 104A, 104B. For example, the switching time of the first andsecond selector switches 102A, 102B may be at least an order ofmagnitude less than the reconfiguration time of the fabric switches 104.For example, the first selector switch 102A and the second selectorswitch 102B may be configured to selectively provide and/or receive asignal to or from (respectively) either the first fabric switch 104A orthe second fabric switch 104B. For example, the first selector switch102A may be a demultiplexer and/or the second selector switch 102B maybe a multiplexer. In various embodiments, the first selector switch 102Ais a 1 to n switch and/or demultiplexer and the second selector switch102B is an n to 1 switch and/or multiplexer. For example, during a firstslot, the first and second selector switches 102A, 102B may provideand/or receive a first signal to/from the first fabric switch 104A. Thesecond fabric switch 104B may be reconfigured during the first slot.After completion of the first slot, the first and second selectorswitches 102A, 102B may be reconfigured such that during a second slotthat immediately follows the first slot, the first and second selectorswitches 102A, 102B provide and/or receive a second signal to/from thesecond fabric switch 104B. The first fabric switch 104A may bereconfigured during the second slot. In other words, while one of thefirst and second fabric switches 104A, 104B participates in atransmission window, the other of the first and second fabric switches104A, 104B participates in a reconfiguration window such that a slot ofthe fast optical switch 100 comprises a simultaneous transmission windowand reconfiguration window rather than the serial transmission windowand guardband of a single fabric switch used as an individual networkelement. In an example embodiment, the fast optical switch comprises nfabric switches 104 (wherein n is an integer equal to or greater thantwo) and the slot may be as short as approximately the length of thereconfiguration time of the fabric switches 104 divided by n−1.

The first and second selector switches 102A, 102B may have a switchingtime t₂. For example, the switching time t₂ may be the time required forswitching the selection of the switch (e.g., the first and/or secondswitches 102A, 102B) switch between a first selection and a secondselection (e.g., to switch between an internal configuration configuredfor providing or receiving a signal to/from the first fabric switch toan internal configuration configured for providing or receiving a signalto/from the second fabric switch, or vice versa). In variousembodiments, the switching time t₂ is less than the reconfiguration timet₁. For example, the first and second selector switches 102A, 102B maybe one-to-two or two-to-one switches. For example, the first selectorswitch 102A may have one input and two outputs and the second selectorswitch 102B may have two inputs and one output. Therefore, in thisexample, the switching time t₂ (e.g., the reconfiguration time of thefirst and second selector switches 102A, 102B) is significantly lessthan the reconfiguration time t₁ (e.g., the reconfiguration time of thefirst and second fabric switches 104A, 104B). For example, thereconfiguration time t₁ may be approximately ten times, one hundredtimes, or a thousand times longer than the switching time t₂. Forexample, in an example embodiment, the reconfiguration time t₁ isapproximately 1 μs and the switching time t₂ is approximately 10 ns.

FIG. 2 illustrates an example of a conventional slot timing 200 for anoptical switch. Each of the conventional slots 206A, 206B, 206Ccomprises a transmission window 202A, 202B, 202C and a guardband 204A,204B, 204C. During the guardband, no data is transmitted. In an exampleconfiguration, each of the conventional slots 206A, 206B, 206C is 10 μslong, each of the transmission windows 202A, 202B, 202C is 9 μs long,and each of the guardbands 204A, 204B, 204C is 1 μs long.

In contrast to the conventional slot timing 200 shown in FIG. 2, FIG. 3shows a slot timing 300 for an example embodiment of the fast opticalswitch 100. Each slot 306 (e.g., 306A-306E) comprises a simultaneoustransmission window 302 (e.g., 302A-302E) and reconfiguration window 304(e.g., 304A-304E). Line 308 indicates which of the first and secondfabric switches 104A, 104B is selected, by the first and/or secondselector switches 102A, 102B to be provided the signal during each slot,The vertical portions of line 308 correspond to the reconfiguration ofthe first and second selector switches 102A, 102B. As shown in FIG. 3,the switching time t₂ (the reconfiguration time of the first and secondselector switches 102A, 102B) is significantly smaller than thereconfiguration time t₁ (the reconfiguration time of the first andsecond fabric switches 104A, 104B). As the switching time t₂ is at leastan order of magnitude (e.g., at least one factor of ten) smaller thanthe reconfiguration time t₁ (e.g., 10 t₂≤t₁), the time duration of aslot 306 is approximately and/or substantially equal to the timeduration of the transmission window 302 and/or reconfiguration window304. For example, the slot 306 is approximately and/or substantiallyequal to the length of the reconfiguration time t₁ of the fabricswitches 104. For example, the guardband is approximately and/orsubstantially equal to the switching time t₂. In various embodiments,the time duration of the transmission window 302 may be approximatelyequal to the reconfiguration time t₁. For example, each of the slots 306may be approximately 1 μs long (e.g., ≈t₁).

In the example shown in FIG. 3, during a first slot 306A, the first andsecond selector switches 102A, 102B are configured to provide a firstsignal to the first fabric switch 104A during the transmission window302A of the first fabric switch 104A and the reconfiguration window 304Aof the second fabric switch 104B, as indicated by line 308. The firstand second selector switches 102A, 102B may then be reconfigured suchthat during a second slot 306B the first and second selector switches102A, 102B are configured to provide a second signal to the secondfabric switch 104B during the transmission window 302B of the secondfabric switch 104B and the reconfiguration window 304B of the firstfabric switch 104A, as indicated by line 308. The second slot 306Bimmediately follows the first slot 306A. In other words, there are noslots between the first slot 306A and the second slot 306B. Thisalternation between (a) the first fabric switch 104A being operated tohave a transmission window and the second fabric switch 104B beingoperated to have a reconfiguration window in parallel during one slotand (b) the first fabric switch 104A being operated to have areconfiguration window and the second fabric switch 104B being operatedto have a transmission window in parallel during an immediatelysucceeding slot continues during the operation of the fast opticalswitch 100. The fast optical switch 100 is referred to as “fast” hereinbecause the switch may be implemented with a slot that is shorter thanthe slot of the conventional slot timing 200.

FIG. 3A illustrates an example slot timing 350 for another exampleembodiment of a fast optical switch 100. The slot timing 350 correspondsto a fast optical switch comprising three fabric switches 104, a firstselector switch 102A that is a 1×3 demultiplexer switch, and a secondselector switch 102B that is a 3×1 multiplexer switch. The slots 356(e.g., slots 356A, 356B, 356M) are approximately and/or substantiallyequal to the reconfiguration time of the fabric switches 104 divided bytwo (e.g., 3−1). Each slot 356 comprises a transmission window 352(illustrated by the white rectangles) and two at least partiallyoverlapping reconfiguration windows 354 (illustrated as the darkrectangles). For example, during a first slot, a first fabric switch 104may experience a transmission window, a second fabric switch 104 mayexperience at least a portion of a reconfiguration window, and a thirdfabric switch 104 may experience at least a portion of a reconfigurationwindow. During a second (consecutive) slot, the first fabric switch 104may experience at least a portion of a reconfiguration window, thesecond fabric switch 104 may experience a transmission window, and athird fabric switch 104 may experience at least a portion of areconfiguration window. During a third (consecutive) slot, the firstfabric switch 104 may experience at least a portion of a reconfigurationwindow, the second fabric switch 104 may experience at least a portionof a reconfiguration window, and a third fabric switch 104 mayexperience a transmission window. During a fourth (consecutive) slot, afirst fabric switch 104 again experiences a transmission window, whilethe second and third fabric switches 104 each experience at least aportion of a respective reconfiguration window. As shown in FIG. 3A, theguardband of the slot 356 is approximately and/or substantially equal tothe switching time of the switching time t₂ and the length/duration ofthe slot 356 is less than the reconfiguration time of the fabricswitches 104.

In various embodiments, as the transmission window of one of the firstand second fabric switches 104A, 104B (and/or additional fabricswitches) occurs in parallel with the reconfiguration window of theother of the first and second fabric switches 104A, 104B (and/oradditional fabric switches), the guardband may be approximately and/orsubstantially equal to the switching time of the selector switches 102A,102B, which is significantly shorter (e.g., at least an order ofmagnitude shorter) than the reconfiguration time of the fabric switches104A, 104B. As the switching time of the selector switches 102A, 102B isat least an order of magnitude shorter than the reconfiguration time ofthe fabric switches 104A, 104B, a fast optical switch may be implementedwith a slot that is approximately and/or substantially equal to (or lessthan) the reconfiguration time of the fabric switches 104. For example,this enables the fast optical switch 100 to be implemented with a linkutilization that is greater than 95%. For example, the link utilizationof the fast optical switch 100 may be 99% or greater, in variousembodiments.

FIG. 4 is a block diagram of at least a portion of an example network400 comprising a fast optical switch 100. In various embodiments, thenetwork 400 is part of a datacenter. For example, the network 400 may bea communication network configured to enable high speed, high capacitycommunication between two or more computing entities, computing devices,computer readable media, processing circuitry, and/or other circuitry.For example, the network 400 may comprise one or more transmitterelements 402, one or more receiver elements 404, and one or more fastoptical switches 100 configured to enable and/or control communicationbetween at least subsets of the one or more transmitter elements 402 andone or more receiver elements 404. For example, the one or more fastoptical switches 100 may be configured to control and/or at leastpartially provide optical links and/or communications paths of thenetwork 400 to enable communication between one or more computingentities, computing devices, computer readable media, processingcircuitry, and/or other circuitry of a datacenter, server network,multiple processor/core computing network, and/or the like. In variousembodiments, a transmitter element 402 is an optical transmitter ortransceiver. In various embodiments, a receiver element 404 is anoptical receiver or transceiver. The transmitter elements 402 and/orreceiver elements 404 may each be part of and/or in communication withone or more computing entities, computing devices, computer readablemedia, processing circuitry, and/or other circuitry. For example, thetransmitter elements 402 and/or receiver elements 404 may each be incommunication (e.g., electrical and/or optical communication) with oneor more computing entities, computing devices, computer readable media,processing circuitry, and/or other circuitry of a datacenter.

For example, a transmitting computing entity 412 may cause atransmitting element 402 to provide a signal to a fast optical switch100. In this example, the first selector switch 102A of the fast opticalswitch 100 receives the signal and passes and/or provides the signal toone of the first fabric switch 104A or the second fabric switch 104Bbased on the configuration of the first selector switch 102A. Theconfiguration of the first selector switch 102A may cause the signal tobe provided to whichever of the first or second fabric switches 104A,104B is experiencing a transmission window 302 in the slot 306 duringwhich the signal is being provided. For example, the first selectorswitch 102A may be configured to not pass and/or provide the signal towhichever of the first or second fabric switches 104A, 104B isexperiencing a reconfiguration window 304 during the slot 306 duringwhich the signal is being provided. Whichever of the first or secondfabric switches 104A, 104B received the signal (e.g., and isexperiencing the transmission window 302 during the slot 306) acts uponthe signal to generate a switched signal. For example, the signal may bepassed from the input of the corresponding one of the first or secondfabric switch 104A, 104B to at least one output of the corresponding oneof the first or second fabric switch 104A, 104B based on the permutation(e.g., the current internal configuration) of the corresponding one ofthe first or second fabric switch 104A, 104B to generate and/or providea switched signal. The switched signal is then provided by thecorresponding one of the first or second fabric switch 104A, 104B to thesecond selector switch 102B. The second selector switch 102B isconfigured to receive the switched signal from the same one of the firstor second fabric switch 104A, 104B to which the first selector switch102A provided the signal. The second selector switch 102B may providethe switched signal such that a receiver element 404 in communicationwith a receiving computing entity 414 receives the switched signal andprovides an indication of the switched signal to the receiving computingentity 414.

In practice, implementation of the fast optical switch duplicates anetwork using optical switches (e.g., fabric switches 104) between thetransmitter and receiver elements 402, 404. For example, implementationof the fast optical switch may create a duplicate network of fabricswitches 104 and selector switches 102 may be added between thetransmitter elements 402 and the fabric switches of the networks ofoptical switches and between the fabric switches of the networks ofoptical switches and the receiver elements 404. For example, two or moreinstances of the same network may be generated, built, and/or the like.For each slot, the selector switches 102 select one of the instances ofnetwork to use for transmitting data during that slot. The otherinstances of the network can be at least partially reconfigured during aslot that they are not being used to for transmitting data. For example,the network 400 may use the fabric switches 104 of an instance of thenetwork on every other slot and that instance of the network willreconfigure during the opposite every other slot (e.g., in an exampleembodiment having two instances of the network).

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

That which is claimed:
 1. An optical switch comprising: two or morefabric switches; a first selector switch; and a second selector switch,wherein the first selector switch is configured to selectively pass asignal to one of the two or more fabric switches, wherein the one of thetwo or more fabric switches that received the signal is configured toprovide a switched signal to the second selector switch, and wherein thesecond selector switch is configured to selectively receive the switchedsignal provided by the one of the two or more fabric switches.
 2. Theoptical switch of claim 1, wherein reconfiguration of the two or morefabric switches is characterized by a reconfiguration time andreconfiguration of the first selector switch and the second selectorswitch is characterized by a switching time, wherein the reconfigurationtime of the fabric switches is longer than the switching time of theselector switches
 3. The optical switch of claim 1, wherein a slot ofthe optical switch comprises a transmission window of one of the two ormore fabric switches that occurs at least in part in parallel with areconfiguration window of the other of the two or more fabric switches.4. The optical switch of claim 1, wherein the two or more fabricswitches have a reconfiguration time and a slot of the optical switch issubstantially equal to or less than the reconfiguration time of thefabric switches.
 5. The optical switch of claim 4, wherein the two ormore fabric switches comprise n fabric switches, n an integer greaterthan or equal to two, and the slot of the optical switch issubstantially equal to the reconfiguration time divided by (n−1).
 6. Theoptical switch of claim 1, wherein each of the two or more fabricswitches, the first selector switch, and the second selector switch isan optical switch.
 7. The optical switch of claim 1, wherein each of thetwo or more fabric switches comprises a collection of switches arrangedin a matrix configuration.
 8. The optical switch of claim 1, wherein atleast one of the first and second selector switches is configured toamplify the signal or switched signal, respectively.
 9. The opticalswitch of claim 1, wherein the first and second selector switches areconfigured to select a fabric switch of the two or more fabric switchesresponsive to at least one of (a) an electrical or optical signal or (b)a wavelength that characterizes a signal to be provided/receivedresponsive to the selection.
 10. The optical switch of claim 1, whereinthe two or more fabric switches are configured to reconfigure to aparticular permutation responsive to an electrical or optical signalindicating the particular permutation.
 11. An optical networkcomprising: at least one optical transmitter element; at least oneoptical receiver element; at least one optical switch disposed in anoptical path between the at least one optical transmitter element andthe at least one optical receiver element, the at least one opticalswitch comprising: two or more fabric switches; a first selector switch;and a second selector switch, wherein the first selector switch isconfigured to selectively pass a signal to one of the two or more fabricswitches, wherein the one of the two or more fabric switches thatreceived the signal is configured to provide a switched signal to thesecond selector switch, and wherein the second selector switch isconfigured to selectively receive the switched signal provided by theone of the two or more fabric switches.
 12. The optical network of claim11, wherein the two or more fabric switches have a reconfiguration timeand the first selector switch and the second selector switch have aswitching time, wherein the reconfiguration time of the fabric switchesis longer than the switching time of the selector switches.
 13. Theoptical network of claim 12, wherein the reconfiguration time is thetime required for a fabric switch of the two or more fabric switches toreconfigure its internal parts in order to implement a differentpermutation.
 14. The optical network of claim 11, wherein the two ormore fabric switches have a reconfiguration time and a slot of theoptical switch is substantially equal to or less than thereconfiguration time of the fabric switches.
 15. The optical network ofclaim 11, wherein the two or more fabric switches comprise n fabricswitches, the first selector switch is a one to n demultiplexer, and thesecond selector switch is an n to one multiplexer.
 16. The opticalnetwork of claim 11, wherein each of the two or more fabric switches,the first selector switch, and the second selector switch is an opticalswitch.
 17. The optical network of claim 11, wherein each of the two ormore fabric switches comprises a collection of switches arranged in amatrix configuration.
 18. The optical network of claim 11, wherein atleast one of the first and second selector switches is configured toamplify the signal or switched signal, respectively.
 19. The opticalnetwork of claim 11, wherein the first and second selector switches areconfigured to select a fabric switch of the two or more fabric switchesresponsive to at least one of (a) an electrical or optical signal or (b)a wavelength that characterizes a signal to be provided/receivedresponsive to the selection.
 20. The optical network of claim 11,wherein the each of the two or more fabric switches are configured toreconfigure to a particular permutation responsive to an electrical oroptical signal indicating the particular permutation.